Light-emitting elements including compounds such as GaN, AlGaN, and the like have many advantages of wide and easily adjustable bandgap energy and the like such that the light-emitting elements may be variously used as light-emitting devices, light-receiving devices, various diodes, and the like.
Particularly, a light-emitting device such as a light-emitting diode (LED) or a laser diode using a compound semiconductor material of a Group III-V or II-VI compound semiconductor can implement various color light such as red light, green light, blue light, and ultraviolet rays with development of a thin film growth technique and an element material, can also implement white light with high efficiency using a fluorescent material or combining colors, and has advantages of low power consumption, a semi-permanent lifetime, a fast response speed, safety, and environmental friendliness as compared to conventional light sources such as fluorescent lamps and incandescent lamps.
In addition, when a light-receiving device such as a photodetector or a solar cell is manufactured using a Group III-V or II-VI compound semiconductor material, due to development of an element material, the light-receiving device absorbs light of various wavelength regions to generate a photoelectric current so that light in various wavelength regions from gamma rays to a radio wavelength range may be used. Further, with advantages of a fast response speed, safety, environmental friendliness, and easy control of an element material, the light-receiving device can also be easily used for power control, a microwave circuit, or a communication module.
Accordingly, application of the light-emitting device has expanded to a transmission module of an optical communication device, an LED backlight replacing a cold cathode fluorescent lamp (CCFL) which configures a backlight of a liquid crystal display (LCD) device, a white LED lighting device capable of replacing a fluorescent lamp or an incandescent lamp, a headlight of a vehicle, traffic lights, a sensor for detecting a gas or fire, and the like. Further, application of a semiconductor device can be expanded to a high frequency application circuit, other power control device, and a communication module.
Particularly, a light-emitting device emitting light in an ultraviolet wavelength range can be used for curing, a medical use, and sterilization by acting curing and sterilization.
A conventional semiconductor device may be configured such that a light-emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer is disposed on a substrate, a first electrode is disposed on the first conductive semiconductor layer, and a second electrode is disposed on the second conductive semiconductor layer.
Light generated in the active layer of the semiconductor device can propagate in lateral and downward directions of the active layer in addition to in an upward direction thereof. Therefore, when light emitted from the semiconductor device travels in the lateral direction, there is a problem in that a traveling path of the light is increased or the light is absorbed inside the light-emitting structure such that extraction efficiency of the light is degraded.